Field of the Invention
The invention relates to a color-matching apparatus for the visual on-light evaluation of flexible copies, particularly for the color matching of multi-color prints.
Color-matching configurations are used in the printing industry for assessing the quality of prints. In such color-matching configurations, a printed product is brought onto a desk-like color-matching table and is compared under defined illumination and observation conditions with a reference copy. In order to prevent errors in color matching, precautions are taken on the color-matching configuration to keep extraneous, interfering light away from the color-matching surface and to prevent the eye of the observer from being disturbed by reflections or other brightness emanating from the illumination source.
Due to the predominantly expected glossy properties of the stocks, color matching should be carried out under illumination at 0.degree. and observation at 45.degree.. In order to obtain a glare-free and reflection-free color-matching surface for printed sheets by using simple and cost-saving means, it is known for the surface of the sheet support facing the observer to be angled by means of a wedge-shaped top part, as in German Patent DE 32 16 991 C2, corresponding to U.S. Pat. No. 4,668,090.
A disadvantage thereof is the fact that the color-matching surface is thus discontinuous, with the result that there is only freedom from glare and reflection in some regions.
In the German periodical entitled: Deutscher Drucker [German Printer] No. 38/26, No. 11, page XIX, a color-matching cabin is shown that is supposed to reduce reflection and glare for the observer, as a result of a concave form of the supporting surface for a printed product. The cabin is encapsulated against extraneous light both at the sides and above the supporting surface. That structure can still be expected to exhibit disturbing glare effects originating from the illumination source inside the cabin.
In the structure disclosed in U.S. Pat. No. 4,173,034, undesired reflections in certain places are prevented by means of displaceable and rotatable diaphragms that are disposed in front of the light source. A disadvantage thereof is the fact that only some regions of the color-matching surface are covered by that structure.
In a control desk for printing presses, it is known for the reference copy to be positioned vertically, with the copy being attached on a support, with the support being adapted to be moved towards and away from an observer, and with the copy also being vertically adjustable. A disadvantage thereof is the fact that it is not possible, for all positions of the copy, to comply with the aforementioned illumination and observation angles, as in Published Japanese Application No. 5-3954.